First step: Add PerforceImportMetadataWidget. Not all functionality is implemented in this version. In order to test it one needs to:

1. Make sure that P4CONFIG is exported to the environment KDevelop is running in
2. Make sure that Perforceplugin is not disabled

The widget makes some very basic tests to
a) See if the perforce client executable is a valid one
b) Test if the specified repository server url is valid
c) Test if the repository contains client workspaces

and reports to the user if any of the tests fail